1. Field of the Invention
The present invention generally relates to sensor carrying floats and, in particular to such floats which have only a limited freedom of movement.
2. Statement of the Prior Art
Instruments and sensors for the detection of underground hydrocarbon contamination have become increasingly popular over recent years due to increased awareness of such environmental pollution. Due to the fact that hydrocarbon liquids have a lower density than water and are, therefore, found at the surface of water, many of the hydrocarbon sensors developed employ a floatation device to maintain a sensor in proximity to the surface of water. Such devices have been adapted for use in oceans, lakes and ground water well shafts. One of the sensors which has been employed with these floatation devices is an electrical conductivity sensor which discriminates between water and hydrocarbon liquids based on the conductivity thereof. Unfortunately, a problem may occur with such sensor and other floatation type sensors, which problem causes a false hydrocarbon liquid signal to be generated when the water level maintaining the device drops to a point where the device is no longer floating. This is due to the fact that the electrical conductivity of air along with the electrical conductivity of hydrocarbon liquids are both less than that of water. Thus, when the water level drops and the device is no longer floating, the electrodes used to measure conductivity are usually exposed to air and, therefore, the conductivity therebetween decreases. This usually causes the instrument to falsely indicate that hydrocarbons are present.